The specific alterations which occur in the control of cell proliferation in chemically transformed cells is being explored in this project. Data from this laboratory, using the nontransformed AKR-2B and C3H/10T1/2 mouse embryo-derived cell lines and the chemically transformed derivatives of these cells, called AKR-MCA and C3H/MCA-58, respectively, have indicated that most of the characteristics of the transformed cells can be accounted for by continuous mitogenic stimulation with a growth factor. Current data indicate that multiple growth-active polypeptides are produced by the cells, some of which stimulate growth in soft agar of anchorage-dependent cells (transforming growth factors), whereas others stimulate growth of cells in a monolayer. Changes in both the production of and response to these endogenous growth factors occur with neoplastic transformation. The data are consistent with the hypothesis that autostimulation by endogenous growth factors can account for the majority of the phenotypic changes in transformed cells. This hypothesis will be further tested by continued purification of the endogenous growth factors by molecular sieve and high-pressure liquid chromatography to separate the different factors and to purify them in sufficient quantities to be used for further studies. The biological activity of the separated growth factors will then be examined, including the quantitation of membrane receptors. Cell cycle arrest point and growth factor and tumor promoter stimulation effects on production of endogenous growth factors will be determined. Production of monoclonal antibodies to the growth factors will be attempted to determine the immunological relatedness of different endogenous growth factors and for use in antibody affinity chromatography for final purification. The role of apparent inhibitors of endogenous growth factors in modulating their activity will also be determined. If autostimulation by endogenous growth factors does prove to be a mechanism of neoplastic transformation of cells, it is possible that the development of inactive analogs or other types of inhibitors may provide a means of controlling the growth of these cells.